How to Estimate a Construction Job

Emily Beach

Construction estimates are developed to determine how much it will cost to build a project according to a set of plans. They are completed by architects, general contractors, and developers both during design and before the project is awarded for contract. While some larger companies may use commercial estimating programs or software, most people still complete estimates by hand, or using spreadsheets. Most estimates are broken down using codes, or divisions created by the Construction Specifications Institute (CSI). CSI codes break the job down into sections based on the trades and materials involved. There are 16 major CSI divisions used in a basic estimate, from Division 1(General Conditions) through Division 16 (Electrical Work). Using these divisions helps the estimator organize the job and makes sure that all costs are covered.

Construction Blueprints

Step 1

Review the entire set of plans and specifications before you begin. Get a picture of what the job will look like, and make sure to compare the specs to the plans in case of discrepancies. Read the scope of work to determine if there are any special conditions or allowances you need to include.

Step 2

Break the project down by division. Many people like to use the 16 divisions provided by the CSI codes, but other systems may work too. Start with site work, or Division 2 (Masonry), and work your way through each aspect of the job. Do a material take-off for each division to determine square footages and the like. A take-off involves measuring the length, width, and depth of each space to determine total quantities of concrete, brick, drywall, and other materials that will be required to complete the job.

Step 3

Determine what materials you will need to complete the job, including equipment rentals and any required tools or supplies. Always give yourself a buffer zone when it comes to materials. For instance, if you calculate that you will need 5,000 square feet of drywall to complete the job, include enough money in your price to cover 5,500 square feet, just in case.

Step 4

Calculate labor required to complete the project. This should be done by division, but should also include laborers, cleanup, and management or supervisory hours.

Step 5

Include costs included under general project conditions. This includes temporary office space, communications, insurance, administrative tasks, and other related expenses. These costs, categorized under the CSI system as Division 1, include all expenses required during the construction process that are not specifically related to materials or labor.

Step 6

Provide an allowance for any items you may encounter that are not defined clearly. This could include excavation, unspecified finishes, furnishings, or equipment. Specify in your bid that you have included these allowances, or list them as alternates for the owner to review.

Step 7

Add all your estimated prices together, then add a percentage for overhead and profit. This number will vary depending on the size of the project and how competitive the bidding process is.